Air bag restraining systems in vehicles for vehicle occupants are known in the art. An air bag restraining device may include a multistage inflator where the stages are actuated at different times in response to vehicle crash conditions.
U.S. Pat. No. 5,935,182 to Foo et al. discloses a method and apparatus for discriminating a vehicle crash condition using virtual sensing. U.S. Pat. No. 6,036,225 to Foo et al. discloses a method and apparatus for controlling a multistage actuatable restraining system in a vehicle using crash severity index values. U.S. Pat. No. 6,186,539 to Foo et al. discloses a method and apparatus for controlling a multistage actuatable restraining device using crash severity indexing and crush zone sensors.
It is also known in the art to sense a crash condition using more than one sensor. A first crash sensor may be used for discrimination sensing and a second crash sensor may be used for safing. Typically, crash values are determined from output signals from the sensors and the determined values are compared against associated thresholds. Only when both the discrimination and the safing determination agree that a deployment crash event is occurring is the associated actuatable restraining device actuated.